Electron-discharge device of the magnetron type



Jul 5,1949.

, P. L. SPENCER 2,475,526

ELECTRON DISCHARGE DEVICE OF THE MAGNETRON TYPE Filed Sept. 26, 1947 Patented July 5, 1949 ELECTRON-DISCHARGE DEVICE OF THE MAGNETRON TYPE -Percy L. Spencer, West Newton, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application September 26, 1947, Serial No. 776,354

2 Claims.

This invention relates to electron-discharge devices of the magnetron type, and more particularly to a cathode structure for such devices and an electrical circuit therefor.

One of the objects of the present invention is to provide a cathode structure, especially suitable for use in a magnetron tube, which requires less power input thereto than has heretofore been necessary to obtain corresponding power outputs.

Another object of the present invention is to provide a cathode structure for a magnetron oscillator which, when once oscillation has commenced, relies for its electron emission, mainly, upon cathode bombardment by charged particles which have absorbed energy from the radio-frequency field developed in the osciliator, said bombardment resulting either in aiding the heating of said cathode to a temperature of thermionic primary emission or the knocking out therefrom of secondary electrons, or both.

A further object of the present invention is to provide an electrical circuit enabling operation, as aforesaid, of a magnetron tube provided with a novel cathode structure such as that above referred to.

In the accompanying specification there shall be described, and in the annexed drawing shown, an illustrative embodiment of the electron-discharge devices of the present invention. It is, however, to be clearly understood that the present invention is not to be limited to the details herein shown and described for purposes of illustration only, inasmuch as changes therein may be made without the exercise of invention, and within the true spirit and scope of the claims hereto appended.

In said drawing, Fig. 1 is a longitudinal sectional view taken substantially through the center of a magnetron tube made and connected in circuit in accordance with the principles of the present invention, the cathode structure of said tube being partially broken away to show the internal construction; and

Fig. 2 is a fragmentary, transverse sectional view taken along line 2-2 of Fig. 1.

Referring now more in detail to the aforesaid illustrative embodiment of the present invention, the numeral Ill generally designates amagnetron tube consisting, broadly, of a cathode structure H, an anode structure 12 spaced from and surrounding said cathode structure, and magnetic means l3 for establishing a magnetic field in the discharge space between said cathode and. anode structures.

The cathode structure I! comprises, referably,

a hollow cylindrical member l4 closed at one end, as at l5, and made of a conductive material which is especially suitable both for primary and secondary electron emission, such as tantalum. The member It is provided with a plurality of staggered transverse slots I6 afiording communication between the interior and exterior thereof, and may be supported at the upper end of a conductive tubular member I! in any desired appropriate manner.

Disposed in the interior of the member I4 is a filamentary member l8 made, preferably, of tungsten, said member being adapted to serve, as will hereinafter be fully explained, as a primary electron emitter, and as a heater for aiding in raising the temperature of the member is to a temperature of thermionic emission. Heating current may be conveyed to the filamentary member l8 from a suitable source of voltage is, controlled by a switch l9, through lead-in conductors 20 and 2| which may enter the device Ii) through the tubular member l1, said conductors being supported in said tubular member as by being embedded in a vitreous seal 22 carried in said tubular member. The cylindrical member 14 is maintained at a positive potential with respect to the filamentary member I8 by appropriately connecting a suitable source of voltage 23 between one of the lead-in conductors 20-2l and the tubular supporting member ll.

The anode structure I2 comprises, preferably, a hollow cylindrical body 24 made of highly conductive material, such as copper, said body being closed at its ends by end plates 25 and 26, the junctions between said body and said end plates being hermetically sealed. Extending radially inward from the interior surface of the body 24 is a plurality of anode vanes 2'5, also made of copper, said vanes being longitudinally substantially coextensive with the cathode member l4, and terminating, radially, a sufficient distance from the surface of the cathode member M to provide an appropriate discharge space therebetween. Each pair of adjacent anode vanes 21 defines, together with that portion of the cylindrical body 24 lying therebetween, an open-ended cavity resonator, all of said cavity resonators communicating, at their open ends, with end spaces 28 and 29 presented, respectively, between the upper ends of the vanes 21 and the plate 25, and the lower ends of said vanes and the plate 26.

Preferably, the vanes 21 are double strapped, for undesired mode suppression, at both ends, as by conductive rings 3 to 3 i clu ive, the 1 19 sealed thereto by means of a second tubular mem ber 11' and a vitreous seall jlg may p ljoj-gct into the device through the end. plate 25., saidlpgle pieces being hermetically sealed to the respective.

plates through which they prpiect, andbeing as sociated with appropriate magnetic means,"not shown, whereby a magnetic field may be .estap; lished through the device in a direction trans- Y9E 1 19 2 5 d si er i ieil tw en h? a hpd? sir We "ena le an st i e I211 Bo er a be er ata froiig the de y ear s ita m ns or exam le a i o l sew 0w 5 e ens ne to t es of t erie/repea e de ned b' he i ees Zl- In perat'io'n, theiswitchfl llj is initially'closed at he fi m n ar i e'r. "t s eate td temperature of thermioni emission by the passage of current therethr ou g'h source of Voltage [9, the emitted primary electrons traveling 1 toward. the cylindrical member I 4 by reason of said cylindrical member, being mainti d at arq ir" mafi wit e e t0 filamentary member by; the source of voltage While some of. these "electrons'will be col leg, .9 y h 'c 1i dr 1,mmb t p ciableinurnber ther twill pass thro'ugh the slo s w d 111112131 Dr maryfemi iori thejfilarnentary member I 18,

,ai ci-br adiaoano "3r m1fI- hQ mr Y l er l in'the 59 11 .e' cay tymsonapog y mil-Mimi? 0f he rr; l pns mime emitted from the filamentary 'rnember It will e. eh hed: a eline? id. rmr ry electrons,

an, somefof thee ctro ns emanate absorb d; s ,energy will be slamme back into the fcy'l i a member t' ii ih ni h i that it C'W ecomes l' qei ar Y. lf ctrons, or tov knock out, secondary" ele'c th re o e. or o l'ihv ligmerim g" he; 'ne fj charge'of the device. Ithas beenfouhd that once" the space charge has been augmented I as ab e, the pOVfer tothedevib l i ftic'idarly', the heating current supplied-by Ithe squrc of.

voltage I9fmayfbe considerably reduced or ieve ii; discontinued, and still enable the generation we. x ms ea i l di' el.

power comparable to that obtainable with the conventional, continually operating cathodes heretofore employed.

This completes the description of the aforesaid illustrative embodiment of the electron-discharge devices of the present invention, together with the mode of operatio thereoi. It will be noted fromIall of, the foregoing that the device is simple and effects considerable economy of operation as compared with what has heretofore been the case in order to obtain corresponding power outputs.

Other objects and advantages of the present inventionwill readily occur to those skilled in theart to which the same relates.

Whatis claimed is:

1 An electron discharge device comprising: a cathode structure; an anode structure, spaced from said cathode structure, and incorporating a cavity resonator; and means, adjacent said un ananqdestruct r t uc ure and ncori ra-Jui eafc v tiii res means djacent: aid. nod st uc d?! H e amaenet qfimdinlth bale. u ecnrsaid athode; ,andnode'ist .u aid cathode structure including a tungsten filament da ted be heatedo-..a,.tempemture it-here mioniovemi sionib -ipa saeeof cu ent h re:

Number Name Date 1,721,395 Hull July- 16, 1929' 1,983,714 Thompson Dec." 11,193+ 2,409,038 Hansen Oct.8;l'19 l 6 2 428393 Blwett 1 Sept: 30; 1941?; 2,438,194 Steele Jr. et'al." Mar, 23, 

